1. Field of the Invention
The present invention relates to generally to orthopaedic implants and more particularly, to bone plates and bone plate assemblies that may be implanted in various parts of the human body to stabilize bone fractures.
2. Description of Related Art
Orthopaedic surgeons frequently encounter bone fractures which require surgical stabilization with implants including metal bone plates having a variety of shapes. Difficulties in the repair of these fractures include insufficient assistance in the operating theater and fractures that are difficult to reduce (i.e., returning the fractured bone segments to their proper positions) and hold. Conventional bone plates may be generally classified as either xe2x80x9ccompression platesxe2x80x9d or xe2x80x9cone-third semi-tubular plates.xe2x80x9d Both types of plates are available in a variety of shapes, for use in stabilizing various bones, and typically include a plurality of interior holes (i.e., spaced apart from the edge of the plate and surrounded by metal) which accept bone screws to secure the plates to the fractured bone segments. Furthermore, both types of bone plates may be somewhat curved in order to accommodate the cross-section shape of the particular bone. Compression plates are typically thicker and the include interior holes are typically xe2x80x9ccompression holesxe2x80x9d having either one or two ramps which extend longitudinally toward the center of the hole from the outer to the inner surface of the plate. The compression holes cause the bone plate to move longitudinally relative to the bone screws used to secured the plate, as the screws are tightened. The one-third semi-tubular plates are relatively thinner and typically include straight-through holes without the longitudinally extending ramps.
Both compression plates and one-third semi-tubular plates have been widely and successfully used to stabilize bone fractures. However, the implantation of either type of plate may be problematic for the surgeon in certain instances.
The bone fracture is approached through a standard incision. Soft tissue such as periosteum, muscle, arteries and veins are partially stripped from the bone to allow visualization of the area and to allow temporary placement of bone clamps and implantation of the bone plate for plates. The surgeon commonly faces situations in which he or she struggles to achieve alignment of the fractured bones with the use of bone clamps, only to have to remove the same implants securing the reduction in order to position and attach the bone plate. After the structure is reduced, the bone segments must then be held in place to allow removal of the clamps to permit placement of the bone plate. In some instances, the fracture may be secured by placing a bone screw across the fracture site.
During the healing process, a so-called sintering of the fracture will occur, which may entail a shortening of the bone in this region. In order to make sure that the fixation with the aid of the osteosynthesis plate may follow this, the screws must move relative to the plate in the elongated holes. Between the screwhead and the hole, however, there is essentially only a point contact place taking place. By virtue of the high surface pressure at the contact points, the screwhead digs itself more and more into the material of the plate and causes an extraordinary high coefficient of frictional adhesion which practically permits the relative movement.
In the past, various patents have issued relating to the use of such bone plate assemblies.
U.S. Pat. Nos. 2,443,363 and 2,486,303 are early bone plate apparatus. U.S. Pat. No. 2,443,363 teaches a bone plate having a plurality of elongated slots through which bone screws are secured. The elongated slots extend on each side of the fracture. U.S. Pat. No. 2,486,303 teaches a curved bone plate also having a plurality of elongated slots on each side of the fracture. Bone screws are inserted into each of the elongated slots.
U.S. Pat. No. 3,604,414, issued on Sep. 14, 1971 to Borges et al., describes an osteosynthesis plate of two-piece construction having a toothed rack system to enable sliding movement of the two pieces in a direction to move the plate pieces in a direction to achieve the greatest approximation of a fractured bone so as to facilitate the joining of the fracture of the bone. The plates are secured to the fragments of the bone by screw members and a tool for moving the plates toward each other.
U.S. Pat. No. 3,659,595, issued on May 2, 1972 to E. J. Haboush, describes a compensation plate for bone fractures including slotted holes on one side of the fracture and slotted holes on the opposite side of the fracture. In particular, a pair of plates are employed whereby one of the plates is located on one side of the fracture and the other plate is located on the other side of the fracture. The elongated holes of each of the plates are overlapped with each other so that the surgical screw can be inserted therein.
U.S. Pat. No. 4,597,497, issued on Sep. 18, 1990 to Hoogland, et al., describes a device for osteosynthesis which includes an elongated bone plate and an elongated slide plate adapted to be fitted to the outside of the bone plate. Several longitudinally spaced elongated holes for the reception of bone screws are provided in one longitudinal portion only of the bone plate. The other longitudinal portion of the bone plate is provided with circular holes and the elongated slide plate is provided with several spaced circular holes.
U.S. Pat. No. 5,234,431, issued on Aug. 10, 1993, teaches a bone plate arrangement consisting of a bone plate with at least one through-opening and a bone screw to be introduced into the through-opening. The bone screw is held to the bone plate by means of a sleeve, which can be fixed in the through-opening of the bone plate independently of the screw.
U.S. Pat. No. 5,951,557, issued on Sep. 17, 1999 to D. W. Luter, describes another type of bone plate having first and second end portions longitudinally spaced from one another and an intermediate portion extending between the end portions. The plate includes at least one interior hole formed in the intermediate portion for receiving a fastener, such as a bone screw, to attach the plate to the fractured bone. A plurality of apertures are formed in the plate, with each of the end portions including at least one of the apertures which extends through the plate from the upper surface to the lower surface for receiving a bone screw.
U.S. Pat. No. 6,280,445, issued on Aug. 28, 2001 to Morrison et al., describes a multi-axial bone anchor system as used for spinal implants. The system includes an elongated member, one or more bone anchor assemblies, and stabilizer members that are fitted within the elongated member. A bone anchor is attached to a bone, and the elongated member and stabilizer are fitted over the bone anchor.
Unfortunately, with these bone fixation plates, where elongated slots are provided, it is common for the surgeon to install the screw in the wrong portion of the elongated slot. As a result, when the bones tend to compress toward each other, the limit of movement of one bone portion with respect to the other bone portion is limited by the length of the slot and the distance from which the screw (as initially installed) moves to a wall of the elongated slot. Since it is important for the bone to compress upon itself for proper healing, a certain amount of movement must be accomplished by the use of the bone plate. Where overlapping plates are employed, it is often difficult for the surgeon to achieve the proper overlapping of the bone plate so that the circular holes can be placed in a proper position with respect to the elongated holes.
It is an object of the present invention to provide a bone plate assembly which effectively assists the healing process by allowing the bone fracture portions to compress toward each other.
It is another object of the present invention to provide a bone plate assembly which assures that the surgeon installs the screw in a proper location.
It is another object of the present invention to provide a bone plate assembly whereby the relationship between the bone plate and the bone tightens as the compression occurs.
It is a further object of the present invention to provide a bone plate assembly which is easy to use, relatively inexpensive and easy to manufacture.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.
The present invention is a bone fixation plate comprising a plate having a first set of openings and a second set of openings, and a plurality of clip members removably fitted respectively into the plurality of the openings of the second set of openings. The first set of openings is a plurality of, circular through holes extending through the plate transverse to the longitudinal axis of the plate. The second set of openings comprises a plurality of elongated holes extending through the plate transverse to the longitudinal axis of the plate. The plurality of clip members within each of the plurality of elongated holes fills a space within the elongated hole so as to allow for the accurate placement of a bone screw therein.
In the present invention, the first set of openings is formed on one side of a center of the plate and the second set of openings is formed on an opposite side of the center of the plate. Each of the first set of openings has a generally constant diameter through the depth of the holes. Each of the plurality of elongated holes has a length dimension which is greater than a width dimension of the hole. Each of the clip members in the respective elongated holes defines an opening of a similar diameter as the constant diameter of the circular through hole. Each of the plurality of through holes has a chamfered area adjacent one side of the plate. Each of the plurality of elongated holes also includes a chamfered portion adjacent the one side of the plate.
Each of the plurality of clip members has a surface extending outwardly of one side of the plate. Each of the plurality of elongated holes has a tapered slot formed in a wall thereof. The plate includes a top side and a bottom side. The tapered slot tapers toward the bottom side in a direction toward the median of the plate.
In the present invention, a first set of screws are respectively received within the first set of openings. A second set of screws are respectively received within the second set of openings. Each of the plurality of clip members resides in removable juxtaposition against the respective screws of the second set of screws.
The present invention is also a method of fixing a break between a first bone portion and a second bone portion comprising the steps of: (1) placing a plate across the break such that the first set of openings is positioned adjacent the first bone portion and the second set of openings is positioned adjacent the second bone portion; (2) positioning a plurality of clip members in the respective elongated areas of the second set of openings such that the clip members define a screw-receiving space within each elongated hole; (3) applying screws through the first set of openings so as to engage the first bone portion; (4) applying screws into the screw receiving space of the second set of opening so as to engage the second bone portion; and (5) removing the plurality of clip members from the second set of openings.
In the present invention, the screws within the elongated holes of the second set of opening slide toward the center of the plate as the first bone portion compresses toward the second bone portion. Also, in the method of the present invention, a tapered slot can be formed in each of the plurality of elongated holes of the second set of openings, a protrusion can be formed on a shank of the bone screws, and the protrusion is fitted into the tapered slot so that the protrusion moves along the tapered slot as the first bone portion compresses toward the second bone portion. In the present invention, the step of removing the clip members includes lifting an edge of each of the plurality of clip members.